Our goal is to develop a platform technology for creating vascularized tissues and organs. A key conceptual framework of this proposal is that blood vessels will not only deliver oxygen and nutrients, but will also provide inductive signals t progenitor cells and thereby stimulate appropriate development of bio-engineered tissues. Such an inductive role for blood vessels has been shown in various biological contexts including pancreas and liver. In this proposal we will focus on building vascularized skeletal muscle tissue as a prototype. We will use three cellular building blocks: endothelial colony forming cells (ECFCs), mesenchymal progenitor cells (MPCs), and muscle satellite cells (SCs). Dr. Bischoff's laboratory has demonstrated the robust capacity of human EPCs and MPCs to self-assemble into perfused vascular networks in vivo - i.e. bio-engineered vessels. Dr. Arany has expertise with SCs and skeletal muscle differentiation, and has identified a novel and powerful angiogenic pathway in skeletal muscle mediated by the transcriptional coactivator PGC-1. SCs are progenitor cells that form multinucleated myotubes and begin to express skeletal muscle-specific genes in cell culture; however, full adult muscle differentiation and organization is not achieved in these conditions. Our hypothesis, supported by preliminary data, is that the interplay between the nascent vascular network built from human endothelial and mesenchymal progenitor cells and the co- implanted SCs cells will result in rapid and more complete skeletal muscle differentiation at the cellular and molecular level. If correct, this would provide a means to construct vascularized skeletal muscle implants for repair of damaged or lost muscle. We will pursue this hypothesis through experiments organized into three specific aims to be conducted over two years, jointly between the two laboratories. Success in these aims will provide a launch point for assessing the ability of these constructs to be incorporated into functional muscle tissue. In addition, the results will provide a novel and innovative platform for vascular-driven parenchymal cell differentiation in tissue engineering and tissue regeneration.